An experiment was conducted to measure the temperature change caused by adding a known quantity of sodium carbonate to an excess of dilute acid. Besides a thermometer and styrofoam cup, these apparatus are available.
1 gas syringe
2 mass balance
3 measuring cylinder
4 stopwatch
Which pieces of apparatus are needed for this experiment?
Source: 2024 AES O Prelim P1 Q1
A student investigates the rate of reaction between an excess of acid of different concentrations and a known quantity of calcium carbonate granules. During the reaction, the student measures the volume of gas released.
In addition to a conical flask and a balance, the following pieces of apparatus are available.
1 gas syringe
2 thermometer
3 measuring cylinder
4 stopwatch
Which pieces of apparatus are needed for this experiment?
Source: 2024 Dunman O Prelim P1 Q1
The setup used to dry gas Q is shown.
What can be deduced about gas Q?
Source: 2024 Jurongville O Prelim P1 Q1
The diagrams show two methods of gas collection.
Which pair of gases can be collected by both methods?
Source: 2026 Dunman O Prelim P1 Q2
The diagram shows an experimental setup to produce and collect a dry sample of gas X.
What is gas X?
Source: 2024 Dunman O Prelim P1 Q2
A student titrated 25.0 cm3 of hydrochloric acid with 0.1 mol/dm3 aqueous sodium hydroxide, using methyl orange. Which step would make her calculated concentration of hydrochloric acid higher than its true value?
2024 Serangoon O Prelim P1 Q16
Tests are done to identify an unknown salt P.
| step | test | observations |
|---|---|---|
| 1 | Dissolve 5 g of P in 10 cm3 of water. | Green solution formed. |
| 2 | To a sample, add aqueous ammonia dropwise and allow it to stand for 5 minutes. | Green precipitate formed, which turns reddish-brown. |
| 3 | To another sample, add nitric acid followed by aqueous barium nitrate. | White precipitate formed. |
What is the formula of salt P?
2024 Zhonghua O Prelim P1 Q20
10.0 cm3 of 1.0 mol/dm3 aqueous iron(II) sulfate was mixed with 10.0 cm3 of 1.0 mol/dm3 aqueous sodium hydroxide: FeSO4(aq) + 2NaOH(aq) → Fe(OH)2(s) + Na2SO4(aq). What did the flask contain when the reaction was complete?
2024 CHIJ O Prelim P1 Q21
An aqueous solution contains 0.01 mol of zinc ions and 0.01 mol of copper(II) ions. Aqueous ammonia is added until in excess. After shaking, the mixture is filtered. What remains on the filter paper?
2024 Bukit View O Prelim P1 Q23
P is a white powdery solid. P dissolved in distilled water to form a blue solution. The solution was divided into two test tubes. In the first, a blue precipitate formed on dropwise addition of aqueous ammonia, which dissolved in excess to form a deep blue solution. In the second, a white precipitate formed on adding an equal volume of acidified aqueous barium nitrate. The mixture was filtered and the filtrate crystallised to give solid Q. What are P and Q?
| P | Q | |
|---|---|---|
| A | barium sulfate | barium sulfate |
| B | barium sulfate | copper(II) nitrate |
| C | copper(II) sulfate | barium sulfate |
| D | copper(II) sulfate | copper(II) nitrate |
2023 Catholic High School O Prelim P1 Q7
A student reacted excess calcium with hydrochloric acid and carried out tests on the reaction mixture. Which observation does not show that the reaction has occurred?
| test | observation | |
|---|---|---|
| A | Add dilute nitric acid followed by aqueous silver nitrate. | white precipitate |
| B | Weigh the reaction mixture at the start and at the end. | mass decreases |
| C | Test the pH of the mixture at the start and after 30 s. | pH increases |
| D | Add aqueous sodium hydroxide until no further change. | white precipitate insoluble in excess |
2024 SCGS O Prelim P1 Q6
Which method would not produce ammonia?
2026 Dunman O Prelim P1 Q16
Measured values of the pressure, volume and temperature of a known mass of a gas are substituted into the ideal gas equation to calculate its relative molecular mass. Which conditions would give the most accurate value of Mr?
| pressure | temperature | |
|---|---|---|
| A | high | high |
| B | high | low |
| C | low | high |
| D | low | low |
2021 YIJC J1 MYE P1 Q14
B2 and 3 only[1]
The known quantity of sodium carbonate is weighed on the mass balance, and the volume of acid is measured with the measuring cylinder.
The experiment measures a temperature change, not a volume of gas or a time, so the gas syringe and the stopwatch are not needed.
A1, 3 and 4 only[1]
The gas syringe measures the volume of carbon dioxide, the stopwatch times the reaction, and the measuring cylinder measures out the acid.
The temperature is not measured, so the thermometer is not needed.
BGas Q is either acidic or neutral.[1]
Concentrated sulfuric acid dries a gas only if the gas does not react with it. It reacts with ammonia, a basic gas, so gas Q cannot be basic.
The setup shows nothing about density, or about solubility in water. The gas bubbles through the acid, so it is not soluble in it.
Chydrogen and methane[1]
Method 1 collects the gas over water, so the gas must be insoluble or only slightly soluble in water. Method 2 is upward delivery, so the gas must be less dense than air.
Hydrogen and methane are insoluble and less dense than air. Ammonia and hydrogen chloride are very soluble in water, and carbon dioxide and sulfur dioxide are denser than air.
Bhydrogen chloride gas[1]
The gas is dried with concentrated sulfuric acid, so it cannot be ammonia, which is alkaline and reacts with the acid. Steam is water vapour, which the acid absorbs.
The gas jar stands upright and the tube reaches its bottom, which is downward delivery, so the gas is denser than air. Hydrogen chloride is denser than air but hydrogen is not.
Brinsing the flask with hydrochloric acid[1]
Acid left in the flask from rinsing adds to the 25.0 cm3, so more sodium hydroxide is needed and the calculated concentration is too high.
A is the right way to prepare a burette, C is the correct end-point, and reading at an angle could make the titre too high or too low.
CFeSO4[1]
A green precipitate that turns brown on standing is iron(II) hydroxide, so P contains Fe2+.
The white precipitate with barium nitrate shows sulfate: FeSO4.
Da green precipitate in a green solution[1]
0.010 mol of FeSO4 needs 0.020 mol of NaOH, but only 0.010 mol is added, so half the iron(II) is left in solution.
Iron(II) hydroxide is a green precipitate and the leftover Fe2+ keeps the solution pale green.
Dno solid residue[1]
Both hydroxides form at first, but both dissolve in excess aqueous ammonia.
Zinc gives a colourless solution and copper(II) a dark blue one, so nothing is left on the paper.
Drow D[1]
The blue solution and the dark blue solution in excess ammonia show Cu2+, and the white precipitate with barium nitrate shows SO42−: P is copper(II) sulfate.
Barium sulfate is filtered off, leaving copper(II) nitrate in the filtrate, which crystallises as Q.
Arow A[1]
Hydrochloric acid already contains chloride ions, so the white silver chloride forms whether or not the calcium has reacted.
Hydrogen escaping lowers the mass, acid used up raises the pH, and the white precipitate insoluble in excess shows Ca2+ has formed.
Bammonium sulfate with an acid[1]
Ammonia is released from an ammonium salt by an alkali, not by an acid.
A is the Haber process, C is the nitrate test, and warming aqueous ammonia drives off ammonia gas.
Crow C[1]
The ideal gas equation is most nearly true at low pressure and high temperature (Chapter 4).
There the particles are far apart and move fast, so their own volume and the forces between them matter least.